The lost message handling is broken in several ways. 1) Clearing the message lost flag is done by writing 0 to the message control register of the object. #define IF_MCONT_CLR_MSGLST (0 << 14) That clears the object buffer configuration in the worst case, which results in a loss of the EOB flag. That leaves the FIFO chain without a limit and causes a complete lockup of the HW 2) In case that the error skb allocation fails, the code happily claims that it handed down a packet. Just an accounting bug, but .... 3) The code adds a lot of pointless overhead to that error case, where we need to get stuff done as fast as possible to avoid more packet loss. - printk an annoying error message - reread the object buffer for nothing Fix is simple again: - Use the already known MSGCTRL content and only clear the MSGLST bit - Fix the buffer accounting by adding a proper return code - Remove the pointless operations Signed-off-by: Thomas Gleixner --- drivers/net/can/c_can/c_can.c | 31 +++++++++++++++---------------- 1 file changed, 15 insertions(+), 16 deletions(-) Index: linux/drivers/net/can/c_can/c_can.c =================================================================== --- linux.orig/drivers/net/can/c_can/c_can.c +++ linux/drivers/net/can/c_can/c_can.c @@ -122,7 +122,6 @@ /* IFx message control */ #define IF_MCONT_NEWDAT BIT(15) #define IF_MCONT_MSGLST BIT(14) -#define IF_MCONT_CLR_MSGLST (0 << 14) #define IF_MCONT_INTPND BIT(13) #define IF_MCONT_UMASK BIT(12) #define IF_MCONT_TXIE BIT(11) @@ -411,27 +410,22 @@ static inline void c_can_activate_rx_msg c_can_object_put(dev, iface, obj, IF_COMM_CONTROL); } -static void c_can_handle_lost_msg_obj(struct net_device *dev, - int iface, int objno) +static int c_can_handle_lost_msg_obj(struct net_device *dev, + int iface, int objno, u32 ctrl) { - struct c_can_priv *priv = netdev_priv(dev); struct net_device_stats *stats = &dev->stats; - struct sk_buff *skb; + struct c_can_priv *priv = netdev_priv(dev); struct can_frame *frame; + struct sk_buff *skb; - netdev_err(dev, "msg lost in buffer %d\n", objno); - - c_can_object_get(dev, iface, objno, IF_COMM_ALL & ~IF_COMM_TXRQST); - - priv->write_reg(priv, C_CAN_IFACE(MSGCTRL_REG, iface), - IF_MCONT_CLR_MSGLST); - + ctrl &= ~(IF_MCONT_MSGLST | IF_MCONT_INTPND | IF_MCONT_NEWDAT); + priv->write_reg(priv, C_CAN_IFACE(MSGCTRL_REG, iface), ctrl); c_can_object_put(dev, iface, objno, IF_COMM_CONTROL); /* create an error msg */ skb = alloc_can_err_skb(dev, &frame); if (unlikely(!skb)) - return; + return 0; frame->can_id |= CAN_ERR_CRTL; frame->data[1] = CAN_ERR_CRTL_RX_OVERFLOW; @@ -439,6 +433,7 @@ static void c_can_handle_lost_msg_obj(st stats->rx_over_errors++; netif_receive_skb(skb); + return 1; } static int c_can_read_msg_object(struct net_device *dev, int iface, int ctrl) @@ -901,9 +896,13 @@ static int c_can_do_rx_poll(struct net_d C_CAN_IFACE(MSGCTRL_REG, IF_RX)); if (msg_ctrl_save & IF_MCONT_MSGLST) { - c_can_handle_lost_msg_obj(dev, IF_RX, msg_obj); - num_rx_pkts++; - quota--; + int n; + + n = c_can_handle_lost_msg_obj(dev, IF_RX, + msg_obj, + msg_ctrl_save); + num_rx_pkts += n; + quota -=n; continue; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/